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The emerging desire for implantable devices assisting individuals’ medical treatments requires their connection to systems placed outside and inside the human body. Their exchange of crucial information on health parameters at different locations may allow them to optimize the patient’s therapy by evaluating the received and transmitted data. Electromagnetic communication methods are the current implementation of choice for such applications. Yet, this kind of communication is often limited to shorter distances due to their restrictions on safe electromagnetic levels, causing no damaging heat dissipation in human tissue. In contrast, employing ultrasound as an alternative method will allow for long-distance communication in the same medium by simultaneously guaranteeing safety requirements for the patient. In this contribution, we will demonstrate a proof-of-concept for which we modulate ultrasonic carrier signals with the help of a low-power consumption microcontroller TI-MSP430. For this, two identical non-focused ultrasonic transducers will be used to receive and send messages through a tissue-mimicking phantom placed in a water tank, indicating the potential of ultrasonic signals as the carrier of information.

The development of a non-invasive, cuffless, continuous, wearable device for the measurement of blood pressure is a complex endeavour due to the high specificity at each measuring site and the need for high accuracy. Proof-ofconcept and validation of a prototype should be performed at an early stage for functionality assessment. Additionally, the emergence of biological computer models allows for in-silico research, which results should be verified in a practical experiment. To grant an optimal preliminary assessment of a prototype, this work aimed to develop and validate accurate in-vitro and ex-vivo arterial models, with simple construction and easily available components. The comparison between a silicone tube and a porcine artery as a mimicked human radial artery was based on the stiffness parameter. Flow pressure is controlled by a centrifugal heart-like pump. Pressure values are extracted with ultrasound and a commercial piezoresistive pressure sensor is used for pressure validation. The porcine artery showed much more realistic stiffness values (·=15.360) than the silicon tube (·=543.420), which was very stiff in comparison to the typical in-vivo radial artery stiffness (·=9.5). The decrease in stiffness of 97.173 % (from the silicone tube to the porcine artery) led to an acute decrease in the derived pressure error. This work serves as guidelines for the development of a low-budget arm phantom, as the simple setup allowed for a primary validation of a proof-of-concept ultrasound-based sensor for the measurement of pressure.

Correct bone screw torque is critical for positive patient outcomes after orthopaedic surgery. Models of the screwing process have been developed to allow a smart screwdriver to optimise the insertion torque. Experimental data is required to test these models, so a test-rig has been developed. Accurate torque measurement is a key part of the test-rig. An FIR filter was designed for this torque signal, implemented on the test-rig, and compared theoretically and experimentally to a mean filter and to no filtering. The FIR and mean filters both performed well, with the FIR achieving better theoretical results, and the mean filter achieving better experimental results. Better understanding of the noise structure and potential signal distortion would be required to improve the FIR filter or to conclusively compare it against the mean filter, however both perform sufficiently well for this application.

High quality recording of neuronal activities and electrical stimulation require neurotechnical implants with appropriate electrode material. Iridium oxide (IrOx) is an excellent choice of material due to its biocompatibility, low electrochemical impedance, superior charge injection capacity, corrosion resistance, longevity, and electrochemical stability. Plasma enhanced atomic layer deposition (PE-ALD) and a suitable precursor, like (Methylcyclopentadienyl) (1,5- cyclooctadiene) iridium, could be a promising technique to produce highly conformal and performant IrOx-films at low temperatures and low costs. Various studies have reported the deposition of iridium oxide, but usually at very high temperatures. These processes are not suitable for polymer substrates and limit the use of such post-processing together with active implants. In this work the (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium(I) ((MeCp)Ir(COD)) precursor was used as a promising approach for depositing IrOx-films using low temperature PE-ALD. This precursor is normally used for chemical vapour deposition processes. First experiments were carried out on silicon substrates at deposition temperatures of 110 C°. The precursor was heated up to 75 °C and oxygen plasma was used as coreactant. The deposited films were analysed with EDX and AFM, showing a smooth surface and a promising ratio between the elements iridium and oxygen.

The demands on flexible implants for recording of neural signals and electrical stimulating have increased in recent years with regard to their functionality, miniaturization, and spatial resolution. These requirements can be met best by embedding powerful complementary metal oxide semiconductor (CMOS) microchips into thin biocompatible polymer substrates. So-called chip-in-foil systems thus combine mechanical properties of a polymer substrate and performance of CMOS technology. The development of a process for direct transfer of multiple CMOS microchips (edge length

Application-specific integrated circuits (ASICs) embedded in polymers have been subject in implant manufacturing for the recent years. The increased functionality combined with good biocompatibility due to flexibility of thin implants makes them interesting for further studies. Thin-film ASICs can be used for the recording and processing of a high amount of biological signals, improving the performance of neural implants. Fabrication and analysis of gold and platinum thin-film connections are subject of this study, especially their capability as high frequency data transmission lines. Three layers of polyimide are used as flexible substrate and insulator of the traces. Various test structures were designed and fabricated, to investigate the resistance and reactance up to GHz frequencies, crosstalk and influence of vias between metallization layers. All conducting structures have a comparable design with a length of 50 mm and a metal thickness of 300 nm, while the line widths were varied. In this configuration gold and platinum thinfilm conductors are both suitable for high-frequency data transmission up to 100 MHz. This transmission frequency limit and impedances are unaffected by a wet environment and in accelerated aging tests. However, both metals show a high pass filter behavior, whose frequency behavior is mostly dependent by the self-inductance and resistance. A simplified ideal transmission model predicts the electrical behavior sufficiently and can be used to design the favored line impedance matching input impedances of the connected ASICs.

Abstract: Terrestrial groundwater travels through subterranean estuaries before reaching the sea. Groundwater‐derived nutrients drive coastal water quality, primary production, and eutrophication. We determined how dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved organic nitrogen (DON) are transformed within subterranean estuaries and estimated submarine groundwater discharge (SGD) nutrient loads compiling > 10,000 groundwater samples from 216 sites worldwide. Nutrients exhibited complex, nonconservative behavior in subterranean estuaries. Fresh groundwater DIN and DIP are usually produced, and DON is consumed during transport. Median total SGD (saline and fresh) fluxes globally were 5.4, 2.6, and 0.18 Tmol yr−1 for DIN, DON, and DIP, respectively. Despite large natural variability, total SGD fluxes likely exceed global riverine nutrient export. Fresh SGD is a small source of new nutrients, but saline SGD is an important source of mostly recycled nutrients. Nutrients exported via SGD via subterranean estuaries are critical to coastal biogeochemistry and a significant nutrient source to the oceans.

Lifetime estimation of implanted electronics in hermetic packages requires the prediction of the humidity induced lifetime. Classical approaches are limited in applications where miniaturized packages and a buffered humidity at low values are being utilized. An approach to overcome these limitations is described and investigations on suitable materials and measurement setups are presented. The findings support the usability of a Zeolite-silicone based desiccant system as a dielectric for a new type of online sensor. The future exploitation of this new sensing principle can allow the monitoring and prediction of humidity conditions inside of highly reliable miniaturized hermetic implantable packages.

An automatized mechanical test has been developed to characterize flexible ECoG and grid electrode arrays under cyclic bending load. Electrodes with different test structures were designed and the bending cycle dependant failure rate was found to follow a Weibull distribution. A corresponding failure mode analysis revealed a characteristic lifetime of more than 25000 bending cycles for some designs. However, design parameters as e.g. a smaller track width reduced this lifetime by a factor of two. In comparison to a similar BMI grid electrode array which was implanted for several months in an animal, failure patterns were comparable to those simulated with the bending test.

Alluvial aquifers represent a vital water resource for many regions. However, understanding and characterizing the interactions between rivers and these aquifers is a major challenge for researchers and water managers. This characterization, in terms of flow velocity or water supply, is important to identify the vulnerability of the aquifers. In this study, our goal is to improve the understanding of interactions between rivers and alluvial aquifers by combining a multi-tracer approach with numerical modeling. By integrating these two complementary methods, we aim to accurately quantify the exchanges between groundwater and surface water, and to identify the water sources contributing to aquifer recharge. This combined approach allows a better quantification of river-aquifer interactions at local scale, in the context of groundwater exploitation by pumping along the river. A large drinking water catchment field located on the banks of the Rhône River, in the southeast of France, was chosen as the study site. This site consists of several pumping wells and observation piezometers parallel to the Rhône. As often, with alluvial aquifer exploitation close to a river, the pumping leads to flow from surface water to groundwater. Groundwater temperature, piezometric levels and river surface water levels were continuously recorded for an 18-month period. During field campaigns, conductivity, stable isotopes of water and radon activity of groundwater and surface water were measured. Radon was applied in a new way to measure the water flow from the river to the aquifer, which reduces the natural radon signal in the aquifer by radon-poor waters from a river. On the site, the radon data clearly delineates groundwater recharge from the river within 50 meters from the banks. The methodology to interpret periodic groundwater temperature signals was extended to the isotopic signal, making it possible to identify the dispersivity in addition to Darcy's velocity. All the experimental data were accounted for in a synthetic MODFLOW model, taking into account the boundary effect of the Ouvèze and Rhone rivers. Model calibration was made using the piezometric records and the PEST package. Reactive transport of radon was implemented using MT3DMS to ascertain the overall water balance of the study site. In addition to the Rhône as a supply, we have shown that the other river (Ouvèze) also contributes of the site's supply (around 55%). By improving our understanding of the interactions between rivers and alluvial aquifers, this study offers valuable insights for sustainable water resource management in regions similar to our study site, i.e., the case of a losing river recharging an exploited aquifer and demonstrates the value of natural tracers, such as radon or stable water isotopes, in situations where the application of artificial tracers is impractical. Our results can guide policy decisions regarding groundwater development and river ecosystem protection. [ABSTRACT FROM AUTHOR]